Development and validation of an online tool to assess perceived portion size norms of discretionary foods

Background: Perceived portion size norms may have shifted toward larger sizes due to widespread exposure to large servings, yet validated tools to assess such norms for energy-dense, nutrient-poor discretionary foods are lacking. Objective: To develop and validate an online image-series tool to examine perceived portion size norms of discretionary foods. Methods: An online tool presenting eight successive portion size options (six for bottled/canned drinks) for 15 commonly consumed discretionary foods was developed. In a randomized crossover laboratory study, adults (18–65 years) reported their perceived portion size norms for each food twice: once using computer-based images and once using equivalent weighed real food options presented at food stations. Agreement between methods was assessed using cross-classification and intra-class correlation coefficients (ICC). Results: Among 114 participants (mean age 24.8 years), >90% of selections were matched in the same or adjacent portion size option. The overall ICC across all foods was 0.85, indicating good agreement. Conclusion: The online image-series tool showed good agreement with real food portion size options and may be valuable for assessing perceived portion size norms of discretionary foods in future research.

Qingzhou Liu, Leanne Wang, Siyi Guo, Margaret Allman-Farinelli, Anna Rangan